1. Field of the Invention
This invention generally relates to optical components generally and more particularly to parallel optical processing within a shared optical component.
2. Description of the Related Art
The telecommunications network serving the United States and the rest of the world is presently evolving from analog to digital transmission with ever increasing bandwidth requirements. Fiber optic cable has proved to be a valuable tool, replacing copper cable in nearly every application from large trunks to subscriber distribution plants. Fiber optic cable is capable of carrying much more information than copper with lower attenuation.
Currently this expansion of bandwidth is being accomplished by what is known as xe2x80x9cwavelength division multiplexingxe2x80x9d (WDM), in which separate subscriber/data sessions may be handled concurrently on a single optic fiber by means of modulation of each of those subscriber datastreams on different portions of the light spectrum. WDM is therefore the optical equivalent of frequency division multiplexing (FDM). Current implementations of WDM involve as many as 128 semiconductor lasers each lasing at a specific center frequency within the range of 1525-1575 nm. Each subscriber datastream is optically modulated onto the output beam of a corresponding semiconductor laser. The modulated information from each of the semiconductor lasers is combined onto a single optic fiber for transmission. As this digital signal is passed across an optical network, it will be subject at various intervals to amplification by, for example, Erbium doped amplifiers and dispersion compensation by, for example, optical circulators with coupled Bragg filters. At each node in the network, e.g. central office or remote terminal, optical transceivers mounted on fiber line cards are provided. On the transmit side, a framer permits SONET framing, pointer generation and scrambling for transmission of data from a bank of lasers and associated drivers, with each laser radiating at a different wavelength. On the receive side, the incoming signals are separated into channels detected by photodetectors, framed and decoded.
Throughout the network a broad range of passive optical components are utilized to process optical beams from individual optical fibers.
Two port devices condition a single beam of light on a single optical path. An isolator blocks feedback to the source of an optical beam. A modulator uses an electro/magneto optic or other property of a crystal/wave guide to modulate a single beam of light passing through it. A filter blocks a portion of the spectrum of a single beam of light passing through it.
Three port devices handle more complex optical functions such as splitting/routing beams based on optical properties thereof. Three port devices, require precise alignment of two/three beams of light across two optical paths.
Circulators separate optical beams on the basis of the direction of their propagation. Thus a circulator can be used to separate the sender""s and receiver""s communications initially duplexed on a single optical fiber.
The multiplexers, demultiplexers, and interleavers are used to separate individual or discrete sets of channels of a WDM communication on a single optical fiber.
The power taps and splitters are used to split a single laser source into multiple optical beams at selected relative intensities.
The polarization beam splitters are used to separate arbitrarily polarized light into orthogonally polarized components. The combiners are used to perform the opposite operation.
The components are expensive to manufacture. In addition, one passive optical component is required for each optical fiber. A typical telecom installation at either the central office or relay site handles thousands of optical fibers each with their own associated passive and active components.
What is needed is a way to reduce the cost, complexity, and form factor(s) associated with providing active and passive optical components to optical fibers.
The present invention advantageously provides a method and apparatus for the parallel optical processing of a plurality of optical beams within a 3 port optical processing unit. The optical processing unit may perform any of the functions associated with the following 3 port devices: a circulator, a multiplexer/demultiplexer, an interleaver, a forward/reverse power tap, a power tap/splitter, a polarization beam combiner/splitter. Access to the optical processing unit is provided by opposing bundles of optical fibers the input and output of which is directed from and to the optical function unit by lenses. Each triplet of optical fibers provides 3 ports of access to the optical processing unit. This allows multiple discrete optical beams each with unique optical parameters, e.g. wavelength, power, modulation, polarization, propagation direction, etc. to be individually delivered, to the optical processing unit on respective optical fibers, to be processed in parallel within the optical processing unit, and to be output individually on the appropriate ones of the optical fibers associated with each of the triplets.
The present invention further advantageously provides optimal and uniform coupling between each triplet of optical fibers, i.e. each discrete set of 3 access ports, with the optical processing unit. This is achieved in part by a precise geometric arrangement of all elements of the apparatus.
The present invention further advantageously provides a reduced form factor and cost when compared with individual 3 port devices.
The present invention also advantageously provides both method and apparatus for improving the performance of a given optical processing unit with respect to any optical beam delivered to it. This improvement results from coupling the appropriate ports of two or more of the triplets to effectively reintroduce to the optical processing unit via the appropriate port(s) of a second of the triplets at least a portion of a beam initially introduced to the optical processing unit through a selected port(s) of a first of the triplets.
In an embodiment of the invention an optical apparatus for parallel optical processing of optical beams on optical fibers is provided. The optical apparatus includes: a first bundle and a second bundle of optical fibers, lenses, and an optical processing unit. Each optical fiber includes a corresponding interface. Across the first and second bundle of optical fibers each triplet of the optical fibers is aligned with a single member of the triplet on one of the bundles and the remaining pair of members in a row on the other of the bundles. The rows formed by the corresponding paired members of each of the triplets align with each other. The lenses direct the optical beams from either of the bundles of optical fibers toward substantially coincident focal points. The optical processing unit processes the optical beams directed by the lenses.
In another embodiment of the invention a method for parallel optical processing of optical beams is disclosed. The method comprising the acts of:
aligning the optical paths substantially parallel with a first axis, with triplets of the optical paths each including a pair of optical paths defining a row and a single optical path and the interfaces of the triplets defining an opposing pair of terminations of the optical paths, with the rows of the triplets substantially parallel to one another;
directing the optical beams from either of the opposing pair of terminations toward substantially coincident focal points between the pair of terminations;
optically processing the optical beams directed in said act of directing.
Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.